OK, I don't have a wiring diagram to confirm this, but I'm pretty sure this is how it goes:

[EDIT - correction - the connector on top of the coil in the photo is the Power Transistor F31. Further explanation in subsequent posts]

Basically the idea is that you have to run +12V power source through the tach before it gets to the coil via the two white wires on your factory tach.

1) Run new wires from your tach (spliced to the ends of the white wires) to your coil.

2) Cut the +12V power source wire and splice the ends of the two wires you just ran from the tach to each side of the +12V source wire you just cut. You can't know which ends to connect at first, so just connect them one way,

3) then plug the connector back into the coil and start the car. If the tach works, then you got lucky your first try.

4) If it doesn't work, switch the ends at the +12V source wire and this time it should work

5) (don't forget to hook up power and ground to the tach itself - green wires out the back i think - you can use the +12V running through the white wires if you want - confused yet?)

If I have time tomorrow, I'll draw a diagram and post it.

Incidently... on the back of the factory tach (under a sticker if it is still there) is a recessed adjustment screw that you can use to fine tune your tachometer. I have an automotive multimeter that has an RPM meter setting that I used as a reference to dial in my tach.

i think i understand but i am a little nervous about cutting the 12v source on the plug to plice the two ends coming from the tach. if you have a chance to sketch something that would be awsome. Is this how you tap into for an aftermarket tach as well? Thanks for the help.

Stock... key turns on power to black/white wire, power is tapped back through the tach, back to the resistor, back to the coil, and on it goes... each time a coil fires, a flyback impuse is observed by the tach sense loop and everything is happy

SR20... ley turns on power to black/white wire, power is run to the central IGNITOR that is used to control power to the coil towers. If you place the Datsun tach into the power line feeding the ignitor, there should be (hopefully) enough flyback impulse energy on the power line to trigger the tach... you will still see the correct number of pulses vs. cylinders, so the tach will read correctly...

arkitekz wrote:does this help? im guessing the black is the ground or -. so that leaves the light green/blk stripe or the other one labeled b/r.

The black is a ground, but it's not the ( - ) side of the coil, that would be the LG/B wire. Is this diagram for your model year? It shows connector F30 only having two wires, and then the ground wire is separate. In any case, you are correct that in this drawing, the wire labeled B/R would be the one to be cut and the tach wires spliced to as I described earlier. I'm glad you're nervous about cutting wires, because I have met too many people who look at wires and think "I wonder what theses are for, they must not be important." and then proceed to hack them out like they were stealing it.

If you wanted to hook up an aftermarket tach, you would tap it (piggyback? if you will) onto the LG/B wire.

It seems to me that this diagram isn't drawn correctly. It appears to show that the high tension coil wire is connected to the primary windings, which is never the case. The high tension wire to the distributor is attached to an iron core in the center of the coil that one end of the secondary windings are attached to. Any electrical engineers out there that can explain how it works as drawn?

I was just at the Nissan dealer looking at their books on your engine which was fairly enlightening.

The three wire connector shown in your photo on top of the coil is the Power Transistor F31 (the 'matchbox' to the L-series EI adopters). Don't mess with that one, as I initially assumed it was connector F30.

Connector F30 is actually two connectors as illustrated in the wire diagram - one has two wires (B/R and LG/B), the other a single black.

The procedure remains as I described earlier, but I just wanted to make sure you knew which physical connector to look for. If you can post a photo showing the F30 connectors, I'd like to see it. It looks like F30 is under F31. Maybe you can disconnect them and take a pic.

Your the man. Thank you for going that extra step and verifying the wiring diagram. I found the correct plug, which was below and it has a lightgreen/blk stripe wire and black/redstripe wire. I am assuming I need to tap into the black/red stripe one. Attached are some pics of the plug. Notice that I thought it was the plug above the ignition coil. It was actually the one below. Also a snap shot of the progress of the ka swap. We are getting ready to do the body work the next couple of weekend and then paint. Will keep you guys posted. Thanks!!! I will check back in when I have time this weekend to hook up the tach.

Holy smokes!! IT WORKED. The two white wires on my dash where already hooked up to a black/white stripe and black/green stripe. So these are the two that I used for the loop system since they were used on my old l-series motor. Thanks guys. Guys on a budget not ready to get aftermarket gauges can do with the stock tach for the meantime. This install took less time than it took me to take the tape off and move the car. HURRRAAAYYYY! Here are some additonal pics.